TEL 



153 



TEL 



similar colours and devices, and a pendant; and any word 

 contained in the table may be expressed by one or two 

 square flags to indicate the number of -the vertical column 

 in which it occurs, and one or two triangular flairs hoisted 

 beneath them, to point out the horizontal column. In 

 case of both the square and the triangular flag; requiring 

 to be doubled at once, instead of the two substitutes, the 

 pendant is hoisted between them ; and if it be necessary to 

 spell any name or word not contained in the vocabulary, 

 the twelfth triangular flag (answering to the square pre- 

 parative signal) is hoisted to indicate that the twenty- 

 four flags are to be taken for the letters of the alphabet, 

 according to a preconcerted order. 



We should not quit the subject of marine telegraphs 

 without adverting to the very important advantages likely 

 to accrue to the commercial shipping interest by the 

 general adoption of a simple and uniform code of commu- 

 nication between vessels at sea, and from them to coast 

 stations, or vice versa. This desirable object is now being 

 greatly promoted by the commercial telegraphic associa- 

 tion superintended by Mr. B. L. Watson, whose signal 

 books are, in future, by the direction of the Lords of the 

 Admiralty, to be supplied to all the government vessels, 

 iji order that they may communicate with such merchant 

 vessels using the code as they may meet with at sea. The 

 whole code consists of thirteen flags, by which any mes- 

 sage may be communicated from one vessel to another, or 

 between a vessel at sea and any of the coast-stations esta- 

 blished by the association at prominent points around 

 the British islands. In connection with these coast sta- 

 tions there are lines of semaphores from the Downs to 

 London; from Holyhead to Liverpool; and from the 

 Spurn to Hull ; and from all of them communications are 

 transmitted to a central office in London, and also to the 

 owners or consignees of vessels entered in the telegraph 

 list ; lor which privilege a subscription of twenty shillings 

 per annum is paid to the association for each vessel. In 

 like manner any message from the owners of a vessel, 

 relative to change of destination, or otherwise, can be 

 communicated from any station within sight of which she 

 may pass. 



Having now noticed the principal varieties of telegraphs 

 which act by displaying Minutls vi.-ible at a distance, whe- 

 ther for use on land or at sea, it only remains, before 

 alluding to contrivances ofa different character, very briefly 

 to touch upon a few points which bear upon telegraphic 

 communications generally, but more especially upon land. 

 The subject has been so ably treated by Sir John Barrow, 

 in the article before alluded to, with the peculiar advan- 

 tages derived from his connection with the Admiralty, 

 that we cannot do better than condense some of hi~ re- 

 marks on the comparative merits of different telegraphic 

 systems. He observes that a telegraph employed for 

 public purposes should be possessed of power, certainty, 

 simplicity, celerity, and secrecy . It should have sufficient 

 power to express, by distinct positions or combinations of 

 moveable parts, any possible order or information, either 

 by letters, words, or sentences. Its certainty will depend 

 upon all its parts being clearly defined, wholly within the 

 field of the telescope, and so distinct that there shall be 

 no risk of mistaking one signal for another ; whence the 

 importance of simplicity becomes obvious. Bearing these 

 points in mind, Barrow conceives that the choice will be 

 iound to lie between the six-shutter telegraph, Popham's 

 semaphore, and Pasley'n universal telegraph. Macdonald 

 thinks that the arms of the semaphore are not so distin- 

 guishable even in clear weather, and not near so visible in 

 cloudy weather, as the boards of a shutter-telegraph ; but 

 Barrow cites some observations of Mr. Gamble, which tend 

 to a contrary result ; making it appear that, owing to the 

 confusion in the image on the retina, occasioned by the 

 refraction of the atmosphere, the property which he terms 

 insul/ilinn is generally more requisite than mere superficial 

 magnitude, to give distinctness to a distant object. This 

 point is illustrated by supposing a person to look at the 

 letter I in the midst of a printed page, and to remove the 

 paper from the eye until the image becomes indistinct 

 limn being confused with the surrounding letters ; and 

 obMTviag how much more distinct the image would appear 

 if the letter were printed alone upon a sheet of white 

 paper. This question however does not rest upon mere 

 theory or analogy; for it is stated that every officer upon 

 the Admiralty line bears testimony to the superior dis- 

 P. C., No. 1507. 



tinctness of the semaphore at all times, and especially in 

 cloudy weather. In order fully to decide the question, 

 the shutter-telegraph at Nunhead, near New Gross, was 

 left standing for some time on the'same hill as the new 

 semaphore ; and the result of the trial for a whole winter 

 was, ' that the semaphore was frequently distinctly visible 

 when the boarded telegraph was so much enveloped in 

 mist and fog that the particular boards shut or thrown 

 open could not be distinguished ;' and that the number of 

 days in the course of the winter upon which the sema- 

 phore was visible exceeded those upon which the shutters 

 could be seen by fully one-third. Even in the six-shutter 

 telegraph one shutter was occasionally mistaken for an- 

 other, and such accidents would doubtless have been more 

 common had a more complicated shutter-telegraph, like 

 that of Macdonald, been employed. The objection urged 

 against the semaphore on the ground of the longer time- 

 taken to move the arms, because they describe arcs of 

 larger circles than the boards of a shutter-telegraph, is 

 hardly deserving of notice, as the difference (which may, 

 Barrow says, amount to one second in each signal) is 

 amply compensated by the greater facility of reading off. 

 The semaphore has also the advantage in the greater sim- 

 plicity of its machinery, which is much less liable to get 

 out of order than that, of the boarded telegraph. 



As shown by the tables given in the previous descrip- 

 tions of the three machines particularly noticed by Barrow, 

 the shutter-telegraph has the power of making a greater 

 number of combinations without the use of the stop-signal 

 (or signal which separates one word or one sentence from 

 another) than either of the others, and Pasley's universal 

 telegraph has the least power ; but this is of little con- 

 sequence, if the lowest power prove sufficient. Although 

 the primary signals of the universal telegraph are only 

 28 in number, they may be increased to 784 by the use of 

 two changes with one stop-signal between them (making 

 three signals in the whole), or, by making three changes 

 (four signals, with the stop), to 21,952; a number con- 

 siderably exceeding the words and sentences in Sir Home 

 Popham's telegraphic dictionary, which do not exceed 

 13,000. As this dictionary has never, it is affirmed, been 

 found materially deficient in any of its divisions of subjects, 

 it is evident that even when applied to communication 

 by words and sentences instead of by letters, Pasley's 

 simple telegraph affords sufficient power for all useful 

 purposes ; and further, that, those who have extended their 

 telegraphic dictionaries to very high numbers (Pasley 

 mentions one extended to 140,000), have impaired then- 

 usefulness, owing to the difficulty and loss of time in 

 finding the required sentence among so many. ' We have- 

 actually seen in one telegraphic dictionary,' observes Sir 

 John Barrow, ' 120 pages, of three columns in each page, 

 and sixty sentences in each column, containing upwards 

 of 20,000 sentences (about one-third of the number of 

 words in Johnson's dictionary), and each of these sen- 

 tences beginning with the personal pronoun " He ;" 20 

 pages witli ' If,'' &c." ' Compared with the use of such 

 a dictionary,' he proceeds to say, ' spelling the sentences 

 is infinitely preferable as to certainty, and in many cases 

 as to celerity. Indeed we should say that the abbreviated 

 nature of communications matie by telegraphs renders 

 spelling by far the most-eligibl'e mode. In clear weather 

 the rapidity of working single signals, the short compass 

 within which any message may be condensed, the impos- 

 sibility of committing any mistake that cannot be imme- 

 diately rectified, more than compensate for the difference 

 of a few minutes which the use of sentences may probably 

 save. In cloudy or foggy weather, the latter method wifl 

 always be liable to mistake. If experience may be as- 

 sumed as a guide, the practice at the Admiralty of spell- 

 ing all sentences, for the last thirty years, must decide in 

 favour of that system.' In making communications alpha- 

 betically, much time may Ue saved by omitting non- 

 essential words and letters, especially vowels. For example, 

 the meaning of the sentence ' Ordr the Agamemnon out 

 of harbour, and direct her to proceed to Spithead,' may be 

 sufficiently expressed by ' Agmcmn. to Spthed.' It, is also 

 important to condense the substance of the communica- 

 tion as much as possible into the former part of the 

 ,-e, so that no serious mistake may arise if the com- 

 munication should be interrupted by foggy weather. 

 Barrow relates a circumstance which occurred during the 

 Peninsular war, in which some anxiety was occasioned by 



VOL. XXIV. X 



